Method of cleaning semiconductor device fabrication apparatus

ABSTRACT

A semiconductor device fabrication apparatus is cleaned after a conductive layer is formed on a metal oxide layer of a substrate. The substrate is disposed on a heater in a process chamber of the apparatus, and the conductive layer is formed by introducing source gases into the chamber. Then the substrate is transferred out of the process chamber. At least one by-product of a reaction between the source gases and the metal oxide layer adheres to a surface inside the chamber, such as to a region or regions of the heater. Once the semiconductor substrate has been transferred outside the process chamber of the semiconductor fabrication apparatus, the by-product(s) is/are removed by evaporation. The by-product(s) can be evaporated using gas, such as one of the source gases, so that the process chamber can remain closed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of cleaning a semiconductordevice fabrication apparatus. More particularly, the present inventionrelates to a method of cleaning the interior of a semiconductor devicefabrication apparatus of by-products produced as the result of forming aconductive layer on a semiconductor substrate.

2. Description of the Related Art

Recently, due to the rapid development of information communicationtechnology and the widespread use of data storage media, such ascomputers, demands have increased for semiconductor devices that operatefaster and have a larger data storage capacity. Accordingly, there is agrowing trend to improve semiconductor device fabrication technologywith the aim of increasing the integration density, reliability andresponse speed of the devices.

In general, a semiconductor device can be made more highly integrated ifa dielectric material formed on a semiconductor substrate of the devicecan be made thinner. However, semiconductor devices become moresusceptible to leakage current the thinner the dielectric materialbecomes. Accordingly, a thin dielectric layer may compromise theoperational reliability of the semiconductor device.

Metal oxides, e.g., Al₂O₃, are typically employed as dielectricmaterials of semiconductor devices. Research into metal oxides having ahigh dielectric constant is actively under way to provide a solution tothe leakage current problem. Specifically, attempts are being made touse a Zr oxide or an Hf oxide as a dielectric material capable ofallowing highly integrated semiconductor devices to operate in areliable manner.

However, the use of a Zr oxide or an Hf oxide as a dielectric materialof a semiconductor device presents several problems. These will now bedescribed more fully with reference to FIGS. 1A through 1D. In aconventional semiconductor device fabrication apparatus, as shown inFIG. 1A, a semiconductor substrate 2 having an Hf oxide (HfO₂) layer isdisposed on a heater 1, and a conductive layer, e.g., a TiN layer, isformed on the HfO₂ layer using NH₃ and TiCl₄ as source gases. Referringto FIG. 1B, although the semiconductor substrate 2 is then transferredoutside the apparatus, oxygen components remain on a region of theheater 1 where they react with the source gases or Hf ions remaining inthe apparatus. As a result, a byproduct layer 3 containing HfN and an Hfoxide is undesirably formed on the heater 1. Likewise, in the case offorming a conductive layer, e.g., a TiN layer, on a Zr oxide (ZrO₂)layer using NH₃ and TiCl₄ as source gases, a layer of byproductcontaining ZrN and Zr oxide is formed on the heater 1.

As shown in FIG. 1C, the process of forming a conductive layer on asemiconductor substrate 2 having an Hf oxide or a Zr oxide is repeatedConsequently, the thickness of the layer 3 comprising HfN and an Hfoxide (or ZrN and a Zr oxide) increases on the region of the heater 1dedicated to support the semiconductor substrate 2.

Japanese Patent Laid-open Publication No. 2003-203907 suggests using achemical vapor deposition (CVD)-based cleaning process to remove thebyproduct layer 3 from the heater 1. However, practice has shown thatCVD cannot completely remove the layer 3. Furthermore, removing thebyproduct layer 3 involves opening the semiconductor device fabricationapparatus periodically. This results in downtime that decreases theproductivity of the semiconductor device fabrication process.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a method of effectivelycleaning an interior surface of a semiconductor device fabricationapparatus of by-products produced as the result of a fabrication processin which a conductive layer is formed on a semiconductor substratehaving a metal oxide layer.

According to one aspect of the present invention, a method for use inthe fabrication of semiconductor devices comprises removing at least oneby-product from an interior surface of the apparatus without opening theprocessing chamber of the apparatus after each time a conductive layerhas been formed on a metal oxide layer of a substrate within thechamber.

First, a semiconductor substrate having a metal oxide layer is situatedin the processing chamber of the semiconductor device fabricationapparatus. Subsequently, the conductive layer is formed on the metaloxide layer by introducing source gases into the chamber. The substrateis transferred out of the processing chamber after the conductive layerhas been formed on the metal oxide layer. The source gases, though,facilitate a reaction with the metal oxide layer wherein a by-product ofthe reaction adheres to an interior surface of the apparatus, such as toa heater of the apparatus on which the substrate is supported. Thesesteps are carried out a number of times such as occurs when processingnumerous substrates.

After each time that a conductive layer has been formed on a metal oxidelayer of a substrate in the processing chamber, and once that substratehas then been transferred outside the processing chamber, theby-products of the reaction are removed from the surface of theapparatus without opening the processing chamber.

According to another aspect of the present invention, the by-productsare removed by evaporating them. Preferably, the evaporating of theby-products is carried out using one of the source gases.

According to still another aspect of the present invention, the othersource gas is then once again introduced into the processing chamber.Thus, the cleaning process not only removes the by-products but alsoforms a conductive layer on the surface of the heater. Once theconductive layer on the surface of the heater becomes so thick as toadversely influence the forming of a conductive, it is removed.

Another object of the present invention is to provide a method ofeffectively cleaning a heater of a semiconductor device fabricationapparatus of by-products produced as the result of a fabrication processin which a conductive layer is formed on a semiconductor substratehaving a metal oxide layer of HfN or ZrN.

The semiconductor substrate is supported on a dedicated region of theheater in the processing chamber of the apparatus. Subsequently, aconductive layer of TiN is formed on the metal oxide layer byintroducing source gases of NH₃ and TiCl₄ into the processing chamber.Then, the substrate is transferred out of the processing chamber.Subsequently, by-products are evaporated off of the heater by heatingthe heater and introducing an additional supply of the TiCl₄ into theprocessing chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the present inventionwill become more apparent from the following detailed description of thepreferred embodiments thereof made with reference to the attacheddrawings in which:

FIGS. 1A through ID are cross-sectional views of the inside of aconventional semiconductor device fabrication apparatus illustrating amethod of forming a conductive layer on a semiconductor substrate havinga metal oxide layer;

FIG. 2 is a flowchart of a first embodiment of a method of cleaning asemiconductor device fabrication apparatus according to the presentinvention;

FIGS. 3A through 3F are cross-sectional views of the inside of aconventional semiconductor device fabrication apparatus illustrating thefirst embodiment of the method of cleaning the apparatus according tothe present invention;

FIG. 4 is a flowchart of a second embodiment of a method of cleaning asemiconductor device fabrication apparatus according to the presentinvention; and

FIGS. 5A through 51 are cross-sectional views of the inside of aconventional semiconductor device fabrication apparatus illustrating thesecond embodiment of the method of cleaning the apparatus according tothe present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A first embodiment of a method of cleaning a semiconductor devicefabrication apparatus according to a the present invention will now bedescribed in greater detail with reference to FIGS. 2 and 3A through 3F.

First, NH₃ gas and TiCl₄ gas are directed towards the entire surface ofa heater 11 inside a processing chamber of the semiconductor devicefabrication apparatus, and a TiN layer 125 is formed on the surfacebefore a semiconductor substrate 12 having a metal oxide layer istransferred into the processing chamber of the apparatus (step S11).This makes it possible to provide processing conditions that ultimatelyfacilitate the forming of a TiN layer 125 on the semiconductor substrate12 during a subsequent step (step S12).

The TiN layer 125 is preferably formed on the entire surface of theheater 11 other than the region that is to be occupied by thesemiconductor substrate 12, as shown in FIG. 3B. To this end, a dummysemiconductor substrate 112 is placed on the region dedicated to supportthe semiconductor substrate 12, and NH₃ gas and TiCl₄ gas are thendirected towards the entire surface of the heater 11, as shown in FIG.3C.

Next, as mentioned above, a semiconductor substrate 12 is transferredinto the processing chamber of the semiconductor device fabricationapparatus. A metal oxide layer having a high dielectric constant, e.g.,a layer of HfO₂ or ZrO₂ is formed on the substrate 12. The Hf oxidelayer is formed using tetrakis ethylmethylaino haffium (TEMAH: Hf[N(CH₃)C₂H₅]₄) or hafnium tert-butoxide (Hf[OC(CH₃)₃]₄) as a sourcegas, whereas the Zr oxide layer is formed using tetrakis ethylmethylainozirconium (TEMAZ: Zr[N(CH₃)C₂H₅]₄) or zirconium tert-butoxide(Zr[OC(CH₃)₃]₄) as a source gas.

Then a conductive layer, e.g., a layer of TiN, is formed on the metaloxide layer (step S12). The TiN layer is formed using NH₃ and TiCl₄ assource gases. To this end, as shown in FIG. 3C, the semiconductorsubstrate 12 is placed on the heater 11 inside the processing chamber ofthe semiconductor device fabrication apparatus where the substrate isheated to 600° C., and NH₃ gas and TiCl₄ gas are introduced into theprocessing chamber.

When the metal oxide layer contains an Hf oxide, the Hf component of theoxide reacts with NH₃, thus forming HfN, and reacts with TiCl₄, thusforming HfCl₄. In this case, the HfCl₄ exists in a gaseous state whereasthe HfN exists in a solid state. As shown in FIG. 3D, a by-product layer14 comprising HfN is thus formed on a region of the heater 11 notoccupied by the semiconductor substrate 12.

Once the semiconductor substrate 12 is moved off of the heater 11 in thecourse of its being transferred outside the processing chamber of thesemiconductor device fabrication apparatus, oxygen remaining on theheater 11 reacts with Hf components that remain inside the processingchamber, thus forming an Hf oxide. In addition, the Hf components thatremain inside the chamber react with NH₃, thus forming HfN. As a result,a by-product layer 13 comprising an Hf oxide and HfN is formed on theregion of the heater 11 that used to be occupied by the substrate 12.

When the metal oxide layer comprises a Zr oxide, a first by-productlayer 13 comprising a Zr oxide and ZrN is formed on the region of theheater 11 that used to be occupied by the semiconductor substrate 12,and a second by-product layer 14 comprising ZrN is formed on theconductive layer 125 over the surface of the heater 11 outside theregion occupied by the semiconductor substrate 12.

Finally (step S13), at least one by-product formed as the result of theprocess described above is evaporated.

When the metal oxide layer comprises an Hf oxide, the Hf oxide and HfNof the first and second by-product layers 13 and 14 can be evaporatedusing TiCl₄. That is, as shown in FIG. 3E, TiCl₄ is introduced into thesemiconductor fabrication apparatus with the heater 11 heated to 600° C.The TiCl₄ reacts with the Hf oxide, thus forming HfCl₄, and furtherreacts with HfN, thus also forming HfCl₄. The HfCl₄ is gaseous and so,the first and second by-product layers 13 and 14 are removed as shown inFIG. 3F.

When the metal oxide layer comprises a Zr oxide, the Zr oxide and ZrN ofthe first and second by-product layers 13 and 14 can also be evaporatedusing TiCl₄. Specifically, TiCl₄ reacts with the Zr oxide, thus formingZrCl₄ and also reacts with ZrN, thus also forming ZrCl₄. The ZrCl₄ isgaseous and so, the first and second by-product layers 13 and 14 areremoved.

As mentioned above, TiCl₄ is used as a source gas in the process offorming the TiN layer. Accordingly, it is not necessary to provide aseparate source of gas for removing the first and second by-productlayers 13 and 14.

The evaporating (step S13) is preferably performed whenever a TiN layer(step S12) is formed on a substrate 12. If the evaporating were notperformed until several TiN layers have been formed, so much of theby-products would accumulate that they could not be sufficientlyremoved. Moreover, forming a TiN layer in the presence of the firstby-product layer 13 could adversely affect the characteristics of theTiN layer, thereby affecting the uniformity of the products produced bysemiconductor device fabrication process.

Hereinafter, a second embodiment of a method of cleaning a semiconductordevice fabrication apparatus according to the present invention will bedescribed in greater detail with reference to FIGS. 4 and 5A through 51.In the following, some aspects of the second embodiment that are thesame as those of the first embodiment will not be described in detailfor the sake of brevity.

First (step S21), a conductive layer 225 is formed on the heater 21 inthe processing chamber of a semiconductor device fabrication apparatusbefore a semiconductor substrate 22 having a metal oxide layer istransferred into the processing chamber. The metal oxide layer comprisesa metal oxide having a high dielectric constant, e.g., an Hf oxide(HfO₂) or a Zr oxide (ZrO₂), and the conductive layer comprises aconductive material, e.g., TiN.

More specifically, NH₃ gas and TiCl₄ gas are introduced into theprocessing chamber of the semiconductor device fabrication deviceapparatus before the semiconductor substrate 22. This makes it possibleto provide processing conditions that ultimately facilitate the formingof the TiN layer 225 on the semiconductor substrate 22 in a subsequentstep.

Preferably, the conductive layer 225 is formed on the entire surface ofthe heater 21 other than the region that will be occupied by thesemiconductor substrate 22, as shown in FIG. 5B. To this end, a dummysemiconductor substrate 222 is placed on the region of the heater 21dedicated to support the semiconductor substrate 22, and NH₃ gas andTiCl₄ gas are then directed towards the entire surface of the heater 21,as shown in FIG. 5A.

Next (step S22), as shown in FIG. 5C, the semiconductor substrate 22 isplaced on the heater 21, and the TiN layer 225 is formed on thesemiconductor substrate 22 by introducing NH₃ gas and TiCl₄ gas into theprocessing chamber. Then the semiconductor substrate 22 having the layerof TiN thereon is removed from the processing chamber. Consequently, asshown in FIG. 5D, a second by-product layer 24 is formed on the heater21 over the TiN layer 225 whereas a first by-product layer 23 is formedon the region of the heater 21 that had been occupied by thesemiconductor substrate 12.

Next, as shown in FIG. 5E, NH₃ gas and TiCl₄ gas are introduced onto theentirety of the exposed surfaces of the first and second by-productlayers 23 and 24 (step S23). As explained above in connection with thefirst embodiment, the TiCl₄ gas reacts with the first and secondby-product layers 23 and 24, whereby the first and second by-productlayers 23 and 24 are removed. Also, as shown in FIG. 5F, a TiN layer 25,225 is subsequently formed over the entire surface of the heater 21.Such a TiN layer 25, 225 is preferably formed on the heater 21 (stepS23) after each time a TiN layer 25 is formed (step S22) on asemiconductor substrate 22.

Preferably, the NH₃ gas is introduced onto the exposed surfaces of theby-product layers 23, 24 before the TiCl₄ gas. That is to say, the TiCl₄gas is preferably introduced earlier than the NH₃ gas by a time intervalsufficient for the TiCl₄ gas to react with the first and/or secondby-product layer 23, 24 and form a gaseous reactant, e.g., HfCl₄.

The TiN layer 25 formed on the region of the heater 21 previouslyoccupied by the semiconductor substrate 22 preferably has a thickness din a range of about 5 to 20 Δ. Next, the TiN layer 25 is removed fromthe heater (step S25).

More specifically, the TiN layers 25 and 225 accumulate on the surfaceof the heater 21 after steps S22 and S23 are performed a number oftimes, i.e., after a number of substrates have been processed, as shownin FIG. 5G. If a TiN layer 25 is formed on a semiconductor substrate 22in a state in which the thickness (dtotal) of the TiN layer 25 on theregion of the heater 21 occupied by the semiconductor substrate 22 isgreater than or equal to 7000 Δ, characteristics of the TiN layer 25formed on the semiconductor substrate 22 may be adversely affected.Specifically, the resistivity of the TiN layer 25 may differ from thedesired resistivity. Therefore, the TiN layers 25 and 225 are preferablyremoved from the heater 21 once the thickness of the TiN layer 25reaches at least 7000 Δ.

The TiN layers 25 and 225 can be removed by introducing a ClF₃ gas intothe processing chamber of the semiconductor fabrication apparatus withthe heater 21 heated to about 300 EC, as shown in FIG. 5H. The ClF₃ gasreacts with TiN, thus forming TiF₄, whereby the TiN layers 25 and 225are removed from the entire surface of the heater 21, as shown in FIG.5I.

As described above, according to a method of cleaning a semiconductordevice fabrication apparatus of the present invention, by-productsproduced in the forming of a conductive layer on a metal oxide layerhaving a high dielectric constant can be removed without opening up the(processing chamber of) the semiconductor device fabrication apparatus.Thus, semiconductor devices can be fabricated with a high degree ofefficiency.

Finally, although the present invention has been particularly shown anddescribed with reference to the preferred embodiments thereof, it willbe understood by those of ordinary skill in the art that the presentinvention may be embodied in many other specific forms without departingfrom the true spirit and scope of the invention as defined by theappended claims.

1. A method for use in the fabrication of semiconductor devices, themethod comprising: (a) providing a semiconductor substrate having ametal oxide layer; (b) situating the semiconductor substrate in aprocessing chamber of a semiconductor device fabrication apparatus; (c)subsequently forming a conductive layer on the metal oxide layer byintroducing source gases into the chamber, the source gases facilitatinga reaction with the metal oxide layer within the processing chamberwherein a by-product of the reaction adheres to a surface of theapparatus within the processing chamber; (d) transferring the substrateout of the processing chamber after the conductive layer has been formedthereon; (e) subsequently repeating (a)-(d) a number of times; and (f)after each time (c) that a conductive layer has been formed on a metaloxide layer of a substrate, and once the substrate has been (d)transferred outside the processing chamber, removing the by-product fromsaid surface of the apparatus without opening the processing chamber. 2.The method of claim 1, wherein said (a) providing of a semiconductorsubstrate comprises providing a semiconductor substrate having a an Hfoxide or a Zr oxide layer as the metal oxide layer.
 3. The method ofclaim 2, wherein said (b) forming of a conductive layer on the metaloxide layer comprises forming a layer of TiN on the metal oxide layer.4. The method of claim 1, wherein said (f) removing of the by-productcomprises evaporating the by-product.
 5. The method of claim 4, whereinsaid (a) providing of a semiconductor substrate comprises providing asemiconductor substrate having a an Hf oxide or a Zr oxide layer as themetal oxide layer.
 6. The method of claim 5, wherein said (b) forming ofa conductive layer on the metal oxide layer comprises forming a layer ofTiN on the metal oxide layer, wherein the by-product comprises HfN orZrN.
 7. The method of claim 6, wherein said evaporating comprisesintroducing TiCl₄ onto the by-product within the processing chamber. 8.The method of claim 4, wherein said (b) situating of the semiconductorsubstrate in a processing chamber comprises disposing the substrate on adedicated region of a heater within the processing chamber, whereby theby-product adheres to regions on the heater not occupied by thesubstrate, and said (f) removing of the by-product comprises removingthe by-product from the heater.
 9. The method of claim 8, and furthercomprising forming a conductive layer on the regions of the heater otherthan said dedicated region without a substrate being disposed on theheater.
 10. The method of claim 9, wherein said forming of a conductivelayer on the regions of the heater comprises forming a layer of TiN onsaid regions of the heater other than said dedicated region.
 11. Amethod for use in the fabrication of semiconductor devices, the methodcomprising: (a) providing a semiconductor substrate having a metal oxidelayer; (b) situating the semiconductor substrate on a dedicated regionof a heater in a processing chamber of a semiconductor devicefabrication apparatus; (c) subsequently forming a conductive layer onthe metal oxide layer by introducing source gases into the chamber, thesource gases facilitating a reaction with the metal oxide layer withinthe processing chamber wherein a by-product of the reaction adheres toregions on the other than over said dedicated region; (d) transferringthe substrate out of the processing chamber after the conductive layerhas been formed thereon; (e) subsequently repeating (a)-(d) a number oftimes; and (f) after each time (c) that a conductive layer has beenformed on a metal oxide layer of a substrate, and once the substrate hasbeen (d) transferred outside the processing chamber, performing acleaning process in which the by-product is removed and a conductivelayer is formed on the heater including over the dedicated region of theheater.
 12. The method of claim 11, wherein said cleaning process (f)comprises evaporating the by-product.
 13. The method of claim 11,wherein said (a) providing of a semiconductor substrate comprisesproviding a semiconductor substrate having a an Hf oxide or a Zr oxidelayer as the metal oxide layer.
 14. The method of claim 13, wherein said(b) forming of a conductive layer on the metal oxide layer comprisesforming a layer of TiN on the metal oxide layer, wherein the by-productcomprises HfN or ZrN, and said (f) performing of a cleaning processcomprises forming a layer of TiN on the heater including over thededicated region of the heater.
 15. The method of claim 14, wherein said(b) forming of a layer of TiN on the metal oxide layer comprisesintroducing TiCl₄ and NH₃ as said source gases into the process chamber,and said (f) performing of a cleaning process comprises introducing onlythe TiCl₄ gas of said source gases into the processing chamber for agiven amount of time and then introducing the NH₃ gas of said sourcegases into the processing chamber.
 16. The method of claim 14, whereinsaid (f) performing of a cleaning process comprises forming a layer ofTiN having a thickness in a range of about 5 to about 20 Δ on thededicated region of the heater.
 17. The method of claim 11, and furthercomprising (g) removing the conductive layer from the heater only oncesaid cleaning process has been performed several times.
 18. The methodof claim 17, wherein said (f) performing of a cleaning process comprisesforming a layer of TiN on the heater including over the dedicated regionof the heater.
 19. The method of claim 18, wherein said (g) removing ofthe conductive layer comprises removing the layer of TiN from the heateronly once the thickness thereof exceeds 7000 Δ at the dedicated regionof the heater.
 20. The method of claim 19, wherein said (g) removing ofthe conductive layer of TiN comprises exposing the layer to ClF₃ gas.21. The method of claim 11, and further comprising forming a conductivelayer on the regions of the heater other than said dedicated region in aprocess discrete from the cleaning process and without a substrate beingdisposed on the heater.
 22. The method of claim 22, wherein said formingof a conductive layer on the regions of the heater other than saiddedicated region comprises forming a layer of TiN on the regions of theheater other than said dedicated region.
 23. A method for use in thefabrication of a semiconductor devices, the method comprising: (a)providing a semiconductor substrate having a metal oxide layer of HfN orZrN; (b) transferring the substrate into a processing chamber of asemiconductor device fabrication apparatus and situating thesemiconductor substrate on a dedicated region of a heater in theprocessing chamber of the apparatus; (c) subsequently forming aconductive layer of TiN on the metal oxide layer by introducing sourcegases of NH₃ and TiCl₄ into the processing chamber; (d) transferring thesubstrate out of the processing chamber after the conductive layer hasbeen formed thereon; and (e) subsequently evaporating by-products off ofthe heater by heating said heater and introducing an additional supplyof the TiCl₄ into the processing chamber.
 24. The method of claim 23,wherein the source gases are introduced into the processing chamberbefore the substrate is transferred into the processing chamber.
 25. Themethod of claim 24, and further comprising situating a dummy substrateon the dedicated region of the heater when the source gases areintroduced into the processing chamber, wherein a TiN layer as a productof the reaction of the source gases adheres to regions of the heaterother than said dedicated region.
 26. The method of claim 23, andfurther comprising (g) subsequently introducing an additional supply ofthe NH₃ and TiCl₄ into the processing chamber after the by-products havebeen evaporated from the heater using the TiCl₄ and while the dedicatedregion of the heater is unoccupied, whereby a layer of TiN is formed onthe dedicated region of the heater.
 27. The method of claim 26, andfurther comprising removing the layer of TiN from the dedicated regionof the heater when the thereof exceeds 7000 Δ.